Deep and shoal alarm



March 9, 1948.

T. F. BLuDwoRn-l DEEP AND SHOAL ALARM Filed Nov. 7, 19.41

2 Sheets-Sheet 1 ATTORNEY Patented Mar. 9, h1948 2,437,416 DEEP AND sHoAL ALARM Timothy Franklin Blud signor to National-S worth, Summit, N. J., as-v implex-Bludworth, Inc., -a

corporation of Delaware.

Application November 7, 1941, Serial No. 418,135

11 claims. (c1. 177-311) Depth nders, by which the depth of Water may be ascertained, have heretofore been invented and are now in use. These'depth finders operate on the. principle of determining the depth by measuring the elapsed time between'the sending of a signal, Which travels to the bottom. of the ocean and isreflected back toa'receiver, and the receipt of the echo, and multiplying this elapsed time by the .rate of travel ofthe sounder signal through the Water. Such devices, however, are not limited to ascertaining the depth of the ocean, but may be employed to ascertain a lateral distance such as a: distanceto'asubmarine or other reiiecting object.

The-object` of. theipresent invention is to providesJ deep and/orshoal alarm to be usedin conjunction With a depth iinder and adapt-ed to give apsignal, eitherraudible and/or visual, when the ship carrying the same is in Water of less than a certain depth and/or to give a signal, either visual and/or audible, when the ship is in Water exceeding a certain depth. For instance, the master or the navigating oiiicer may desire a signal to be given'in case his vessel should pass into shoal water of less than fty fathoms. One ofthe. objects .of the invention is to provide means whereby the ofiicer could adjust the mechanism so as to give a signal Whenever the vessel Was inwater of less than this depth, or the ocer might desire for a signal to be given in case the vessel should sail intolwater exceeding some predetermined depth, suchas sixty-five fathorns. One of the objects ofthe invention is to provide'means whereby' a signal Will be given under` the conditions recited.

Another object of the invention is to provide ashoal alarm which gives acontinuoussignal from the time the echo is received until the come pletion of a cycle of'events and then will be rendered inoperative at the completion of a cycle of events.

Another object ofthe invention is. to provide means to renderthe shoal alarm inoperative when the vessel is in water exceeding a predetermined depth.

Another object of the invention is to provide a deep alarm Which'vvill operate continuously from the time certain parts reach a position corre, spending to a given depth until the end'of a cycle of events, and means to prevent the operation of the deep alarm in case the vessel is in shoal Water.

Another object of the invention is to provide a relay control circuit to render the deep alarm inoperative when the vessel is in shoal water and torender the shoal alarm inoperative When the vessel is in deepwater.

Another object` of :the invention isthez provision of control means to govern each of the alarms; the said control .meansb'eing in turn. controlled'fby the receipt of the echo.

Another object of the. invention'` is. to` provide rotatable cam discs which .control the., operation of `'the relayv circuits, forming 1.a' part of boththe deep and the sho-al alarmsvstems, andto provide adjustable contactmeans .whereby the deep-and shoal alarms may be adiustedto .various depthslas` determined. by theoicerin charge.;

Other. objects and advantages of the invention will appear nthedetailed specification andclaims which follow.'

The: invention maybe better understoodlsbyrefferring :to the :attacheddrawings in. which'n Figure. 1. is a sidexelevational viewof'one eme bodiment ci' theinvention, and includingtheelece tric circuits therefor:

Figure 2 is a perspective elevational` the rotatable drum type shutter.

Figure. is a view similar toFigure 2, but shovvr ing the shutter'when rotated to .a different position from. that .shown inFigure 2.

Figure 4 is a. plan view of how theshutter would appearV iiiit were cut longitudinally. andunrolled intoazflat sheet, and

Figure 5 is a side'elevation-al viewfof theindex plateV and showing indotted lines a portion `ofthe continuously*rotatingcam disk andthe adjuste able disc behind the plate: Y

Referring: now in detail vto thedrawings; asupf port 41 is 1 provided on which are mounted' the motor.M,.bracketsf48, i9; 5S, .5i and 52. Theme.- tor M :drives: ai pinion 53, Vwhich meshes with and drives. a'. gearV 5A `secu-recite a shaft 46, the said shaft extending through the. brackets` 48, 139;,58 an-d 51, and at the uppenend of thesaidshaftais secured the rotatable shutter'. The construe,-

view of tion of; this shutter may be .better understood .by

referring` to Figure 4, showing va plan viewthereof When unrolled.v It will be noted; that there -isan opaque: p ortion 56V and a translucent. portion 7 5?! with a diagonaldivision. line 58 separating; the opaque 'and the'translucent portions. It will furither be notedthat the-diagonal division linef is not a true diagonal, for itV extendsfromwthe point A to the point B, and there is an opaqueporftion 59. at the4 extreme 'bottom'.V 'l'hepoint A, is spaced slightly tothe left of the verticallinex, and the point B; isspaced downwardlya short disitance below'thezfextreme top of the opaque-pori tion; As .Willhereinafterfbe described, when y.the 'pointA reaches .thezero position ofitheslot 61;.in

the" cylinder 62,'. the signal.` would: be.; sent 1 out.

the shutter is continuously rotated, the signal will be sentvout when the opaque portion thereof is behind the slot 6I, that is just at the instant that the point A of the shutter reaches the zero point of the slot. The signal will then travel toA the bottom of the ocean, and the echo will, by means hereinafter to be described, cause a neon tube II to be extinguished, and the observer can read on the indicia 63, while the light is burning, the position of the upper portion of the line 58 showing the then instantaneous depth of the ocean, the shutter rotating from left to right.

Secured to the shaft 46 are cam discs I, I9 and 33 provided respectively with cams 64, 55 and 66. Adjustable contact carriers I8, 20 and 34 are adjustably supported on the brackets 50, 49 and 48 respectively. The adjustable contact carrier I8 is adapted to be manually adjusted on the bracket 50 and to be held by the said bracket in its adjusted position. This contact carrier I8 i-s usually adjusted only a, few degrees to the right or left of zero. It may be used to correct known variables, such as the height of high tide or low tide or the squat of the ship, or to make allowance for the distance that the bottom of a ship is below the surface of the water. It is mounted behind an index plate 51 having a Window 68 therein. When the zero appears at the center of the window 68, it means that no allowance is being made for the variables such as tide, etc., and when shifted to the right or left, itv will indicate the number of feet or fathoms of the adjustment. This variable contact carrier I8 is provided with a contact carrying arm 69, which carries the reset contact arms 6 and 1, and the contact arms 3a, 2, 3b, 4 and 5, it being noted that the contact arms 6 and 1 are slightly to one side of the vertical plane through the remaining contact arms, so that as the cam 64 rotates in the direction of the arrow, or counterclockwise, the said cam 64 would first contact the reset contact arm 1 and shortly thereafter would contact the contact arm 2. As a matter of fact, the cam 64 reaches the reset contact arm 1 at the time the vertical line 60 passes the slot 6I, and the cam 64 would reach the arm 2 when the shutter had been rotated, so that the point A would be at the zero point of the slot 6I. The sending of the initial signal will now be described. When the cam 84 on the disc I reaches the arm 2, it moves the said arm 2 upwardly out of contact with the arm 3a and into engagement with the arm 3b. On the left hand upper end of the arm 2 is an insulation plate 10, which, when the arm 2 is moved upwardly by the said cam 64,

moves the contact arm 4 upwardly and simultaneously, making contact between the arm 4 and the arm 5. It will, of course, be understood that these are only momentary contacts while the cam 64 is elevating the contact arm 2. The contact between the contact arms 2 and 3b completes the circuit through the capacity I2c and through the Vtransmitter I2 which projects a signal, either sonic or supersonic, towards the bottom or other surface. The instant that the cam 64 passes from beneath the arm 2, this circuit i-s broken. The function, therefore, of the circuit including the arms 2 and 3b is to send the signal at the moment the cam 64 reaches the arm 2, which is at the vsaine instant that the point A of the shutter .reaches the zero point of the slot 6I. To switch arm 4 is applied a negative potential from the electric source I1. When the switch arm 4 is raised into contact with the switch arm 5, the circuit is completed to the relay winding 8, which attracts armature 8a, thereby establishing contact between the contact 9 and the armature 8a, and between the contact Illand the armature 8a. Current can then pass from the source I1 through the armature 8a and contact 9 to the winding 8 after the momentary contact between 4 and 5 is broken, so that the armature 8a will continue to bridge the contact points 9 and I0. It will also be noted that a negative potential is applied to i the contact Ill, which completes the circuit through the neon lamp I I, so that the light shines through whatever translucent portion of the shutter which appears behind the slot 6I.' As this shutter continues its rotation, with the neon lamp burning, it appears that a rectilinear column of light rises upwardly lfrom the zero point to the point at which it may be extinguished. The moment that the cam 64 on the disc I disengages the arm 2, contact is re-established and maintained between the contact arms 3a and 2, and negative potential is thereby supplied to the capacity I2c until the beginning of the next cycle, that is until the vertical line 60 reaches the slot 6 I.

When the signal is transmitted by the transmitter I2, the said signal travels toI the bottom of the ocean or other reflecting surface, and is reflected back to the receiver I3. It is well known that such receivers, when actuated by the echo, cause the transmission of a weak electric impulse, which is amplied by the amplifier I4, and energizes the relay winding I5, thereby attracting the armatures I5a and I5b, that is, it moves the armature I5b into engagement with the contacts Ib and Id, and moves the armature I5a into contact with the contacts IGa and I6c. The armature I5a thereby short circuits the relay winding 8, releasing the spring loaded armature 8a and opening the contacts between 8a and 9 and 8a and I0, thereby breaking the circuit to the neon lamp II, so that it is extinguished. It will, therefore, be noted that the neon lamp i-s illuminated at the moment the signal is sent out, and is extinguished at the moment of the receipt of the echo.

I have now described the means by which the signal is transmitted and received, and how the depth of the ocean is visually indicated. If it is desired to make allowance for the fact that the receiver and transmitter may be positioned in the hull of the boat a known depth beneath the surface of the water, such an adjustment may be made by rotating the adjustable contact carrier I8 and thereby moving the position of the various contacts carried by the arm 69, so that the signal will be sent out at a time not exactly corresponding to the point when A would appear at the zero of the slot or window. This allows for any desired adjustment of this nature.

Just before the completion of the cycle, the cam 64 would contact the arm 1 and would raise it out of engagement with the arm 6. This would be only momentarily. It will be noted that the arm 6 is connected to the negative pole of the source of electric supply, and that the arm 1 is connected to the contact 30, contact arm 22, and other contacts, the function being to de-energize and reset the alarm system, as will hereinafter be described. This occurs while the shutter is rotating from the vertical line 60 to the position occupied by the point A.

In describing the deep and shoal alarm, the description may be simplified by using an illus- 57 tration; As viewedv in Figure 1, an indicated ,deptl'iV of a little less than sixty fathoms is noted. Let /us `call the upper portion of the line 58 visiblehin the Window by the reference character E. Lotus-further assume that the navigating oiicer would-,like for a signal to be given if the ship should bein water of less than iifty fathoms. We' will' call this the shoal alarm. Let us further assume that he would like another indicationtobe given if the vessel were in water'exceerglingVV sixty-five fathoms. We will call this the'deepV alarm. -This would be very similar to the semaphore arm as used on railways showing redifor` strop or great caution, yellow for caution andgreen` forV all clear. Just so in my proposed system the shoal alarm indicates great caution, theino alarml indicates caution `and the deep alarm; indicates there is no danger as to depth. Obviously, the `navigating officer can adjust these 'gures to any gures he may desire, by corre- 'spondinglyadjusting the adjustable contact carriers 26 and 34, but as above stated, it makes it simpler'to understand if we assume that he has decided upon certain figures and has adjusted his adjustable contact carriers accordingly. I have, therefore, shown the shoal alarm contact carrie'r34 as adjusted to fty fathoms, and the deep alarm contact carrier as adjusted to sixtyfi've fathoms, it being understood that these figures would appear behind the windows like the window 682 in the index plate 6l.

The deep alarm will now be described. The deep alarm may be described as an arrangement of` cam operated and relay operated contacts which control the ilow ofelectric current through relays, Iamps bells, buzzers, or other circuit closing or `alarm devices. While I have shown a solenoid type relay, itis of course understood that any other type of suitable relay might be employed.` In substance, the electrical circuits are so designed that a deep alarm will be set off and maintained continuously when the vessel'is in deep water and from the time certain parts reach'. a position corresponding to a given depth until, the time of the resetting of the circuit, the safidcircuit` being reset immediately prior to the Zero point of the indicator or the beginning of ainewrcycle... `The adjustable contact carrier 2li hasbeen set to indicate sixty-five fathoms, and this. carrier carries a contact carrying arm H, which arm carries contacts 2l and 22, the contact.` 2l `being positioned below the Contact arm 2'2/and in the path of movement of the cam 65 ori-the disc i9 which, it will be remembered, rotastes` with the. shaft dt. When the cam S contacts the. arm 2|, it raises it into contact with the arm 22. If 'the depth measurement exceeds sixty-five'fathoms, the cam 65 will have passed thearm 2|. ybefore the armature ib closesthe contacts. lib and ltd, and the deep alarm will bey sounded, but ii the depth is less than sixtyflve athoms, the cam 55 will not have closed the contact arms 2i and 22 `when the echo is receivedand the deep alarm will not be sounded. In other words,v the deep alarm will be actuated inthe. indicated depth ismore than sixty-ve fatlioms,` but Will not be actuated if it is less than sixty-rive fathoms. It will be noted that the illustrated adjustment of the deep alarm is sixtyiive4 fathoms. Referring to the case just stated, the echo signal` has arrived when the indicator showssixty fathoms, and it has extinguished the light source IVI. When the echo was received, the relay'winding, l5 was energized, as above described, and the armature Ib bridged the contact-s lsb and ftd' se that thel negative terminal of the source of electric currentl was oonnected through the `contactVv |617, armature |511,-

and contact l'6d, therebyA applyingenegativepotenti'al to the relay winding'N; thereby attract'-A ing the armature 26' and closingcontacts 29 and 39. Of course, the armature li is attracted' only momentarily at the moment ofthe echo, and it is necessary to providemeans toV maintain the armature' 26 `in: position-'to close the contacts 29 and 30- afterthe' armature ISf moves away from the contacts llfand Id, andthisis done through. the circuit, includingthe' armsk 6 and 7. The contact arm `(i is in' circuit withfa-negative pole ofthe source of` 'electricsupplyV andthe contact armA 'I is in engagementrwith' the arm 6, which is in' circuit with the contactv 30, from'Y which a negative potential passes'through the armaturel 26, contact 29,' and to-thewfndingy21',' thereby maintaining thev Wind-ing 21'energize'd until the reset. contact arm `T is raisedfby the cam 64. When the armature 26 isbri-dg'ing the contacts 29 andl 36, it has brokenl the circuit through the contact 28, thereby inhibiti-ng'relay winding 23, so'that when cam 65 'moves the contact arm 2f into' engagement Vwith the contact arm 22, the relay'23 does' notoperate'.

However, the deep alarm will" operate if'j'the measured depth had exceeded sixty-dye fathoms; and' in such a case its operation would be asfollows: If the water 'exceeded'sixtyL-ve'fathoms; the cam 65y would have; passed the ccntactarrn 2l before the echo. was received,v and' therclosng,V of contact arms 2| and 2'2`Will' energizerelay Winding, 23 through armaturez and' contact23; In that case the contacts 2l' and 2.2 would' have been closed'prior to they movement "of the armature |519 into contact with the contacts |617' and ld, so that the coil' 21 would 'not be energized, and the negative potential would Dass from the negative pole of the battery l"| through. thecontact arm 6 and contact arm 1', and'to' the. contact arm 22 and contact arm 2li', andl thenceV through the armature 26 to contal'st28` and-Winding 231,` thereby pulling downwardly the double armature 24, 25. The armaturev 2'4"wil1'ftherr. bridge' con: tacts 12 and 13' while th'e armature 25 willbridge' contacts 'M and T5. However; the moment that the cam 65 passes beyond thev contact arm 2f the circuit will be .brokenv and it 'is necessaryto maintain current through the Vwinding 23 until the. end of the cyc1e.so that; the d'eepalarm will continue to sound.' The contacts 12 and T4' are directly connected'. to the contact arm. 1', so that these contacts have a negative,potential.V When' the armatures 25 and 2id have been,mov'ed"down' wardly into engagement with the contacts 15' and 74, and 13 and T2 respectively, the light 3l' and the bell 32 will be energized and' current'will pass from the contact 'l'2jthrougl'1 thek armature 2,4 tocontact 13, and to the winding 23 thereby maintaining the armatures in.. closed' position until the end of the cycle, at'f which .time the arm 'i is raised out of contact wth1tlie`arm/6, and that circuit isV broken, so., that. the"deep alarms 3| and 32 .will` thereby. (1) not be excited if we are in. Shoal: Water., this; beingv prevented by the armature 2B being moved out of. en. gagement with. the contact. 28. and 62) will be excited if the ship. is in. deep water,` and will continue to be excited from the. time the contacts 2| and 22` are closed until thearm` lis. moved out of engagement with. the arm, 6 at ornear the end of the cycle., The armature,.261tl'iereel fore, serves as a means tc inhibit the operation Zr ofthe deep alarm whenl the vessel is in shoal water, and serves as a part of the circuit to the deep alarm in case the vessel is in deep water.

The shoal alarm will now be described. The drawing shows the adjusted shoal alarm set at fifty feet. Suppose the indicated depth is some value less thanfiifty feet. The echo received by the receiver I3 will energize the relay winding coil I through the receiver amplier I4, thereby closing the armature I5b to contacts IBb arid IId, sothat a negative potential passes to the armature 16 and to the contact 38, which is in circuit with the relay winding 4I, thereby attracting the armatures 42 and 43, so that the armature 42 bridges the contacts 11 and 18, and the armature 43 bridges the contacts 19 and 80. However, the current will iiow through the armature I5b only momentarily, so that armatures 42 and 43 will be moved into contact with the said contacts 18 and 11, and 19 and 8D respectively, only momentarily insofar as the circuit through the armature I5b is concerned, but it is necessary to maintain the winding 4I energized. However, the moment that the armatures 42 and 43 are moved into engagement with their respective contacts, the negative potential on thearms 6 and 'I will be transmitted to the contacts 18 and 80. From the contact 18 this negative potential will pass through the armature 42 to the Contact 11, and thence to the winding 4I, maintaining it energized while the negative potential from the contact 8D will pass through the armature 43 to the contact 19, and thence to the shoal lamp 45 and shoal bell 44, so that the light will be illuminated, and the bell rungas long 4as the said circuit remains closed'. However, this circuit will be broken when the rcam 64 raises the arm 1 out of engagement with the arm 6, which is at the end of the cycle.

Conversely, suppose the indicated depth is greater than -fty feet.. In that case, the shoal alarm should net operate. In such a case, the cam 66 on the cam disc 33 will have passed the arm 36 and raised it into engage-ment with the arm 35, prior to the receipt of the ec-ho, thereby energizing the relay coil 31, the circuit being completed from the negative pole of the source of electric current through the arms E and 1, and through the arms 35 and 36. When the coil 31 is energized, it attractsthe armature 16 tothe contacts 39 and 49, and away from the contact 38. The circuit through the contacts 35 and 36 is of cours'eimmediately Athereafter broken, but the moment the armature was moved into engagement with the contacts 39 and 4G, a circuit was closed from the source of negative potential through the arms 6 and 1 to contact 39, and through the armature 13 to contact 40 connected to the winding 31, so that the solenoid winding 31 is maintained energized, and the circuit through the contact 38 is opened. If

now the signal should return with the circuitv through th'e contact 38 broken, the coil 4I would not be energized, and there would be no closed circuit to the shoal alarm, and it would, therefore, remain inoperative.

At ornear the end of the cycle of operation or one complete rotation of the shutter, the arm 'I is raised out of engagement with the arm 6, and all connection to the relays 21, 23, `"II and 31 are broken, so that the entire mechanism is thereby reset and is ready for a new cycle of operation, avcycle of operation being one complete rota tionof the shutter. However, the

invention is not limited to a rotating shutter, -for the invention may be applied to any type of depth nder. A more accurate deflnition of cycle would, therefore, be the events which occur between the sending out of successive signals.

It is realized that many changes may be made in the speciiic form of the invention shown by way of illustration herein, and`I, therefore, desire to claim the same broadly, except as I may limit myself in the appended claims.

Having now described my invention, I claim:

l. In a depth finder, a lamp, a signal transmitter and a receiver adapted to receive the echo from the transmitter,` circuits for said lamp, transmitter and receiver, a constantly rotating cam means, contacts actuated by said cam means on the zero point of its rotation to close the circuit to the transmitter and the circuit to the lamp, means to maintain the lamp circuit closed unt'il the echo is received, means to open the lamp circuit when the echo is received, a deep alarm, means to operate the deep alarm when the depth exceeds a predetermined value, and to prevent its operation when the depth is less than said predetermined value, said last named means including a relay, means whreeby the relay when operated continues to be operated until reset, and means controlled by said cam means to reset the relay when the cam means has almost completed its revolution.

2. In a depth finder in which signals are sent out lby a transmitter and the echo is received by a receiver, the interval between two successive signals being one cycle, a deep alarm, a relay controlled by the echo at the moment the echo is received, a circuit closed by the momentary actuation by the echo of the relay, said circuit including the windings of the relay and thereby maintaining Athe relay actuated, a constantly moving cam which passes through its zero position at the moment the signal is transmitted, contacts adapted to be closed by said cam when the cam has rotated to a point representing a given depth, means to actuate the alarm if the said contacts close prior to the actuation of the relay and to prevent the actuation of the alarm if the contacts close after the actuation of the relay.

3. In a depth finder in which signals are sent out by a transmitter and the echo is received by a receiver, the interval between two successive signals being one cycle, a deep Ialarm, a relay controlled by the echo at the moment the lecho is received, a circuit closed by the momentary actuation by the echo of the relay, said circuit including the windings of the relay and thereby maintaining the relay actuated, a constantly moving cam which passes through its zero position at the moment the signal is transmitted, contacts adapted to be closed by said cam when the cam has `rotated to a point representing a given depth, means to actuate the alarm if the said contacts close prior to the actuation of the relay and to,

prevent the actuation of the alarm if the contacts close after the actuation of the relay, and means to reset the relay at the end o f the cycle.

4. In a depth nder in which signals are sent out by a transmitter and the echo is receivedby -a receiver, the interval between two successive signals being one cycle, a deep alarm, a solenoid, an armature therefor, a circuit to said solenoid, means whereby said circuit is closed upon the receipt of an echo, a second circuit to said solenoid, said armature serving as a means to close said second circuit when the solenoid is actuated by the said current in the first circuit, a constantly moving cam which passes through its zero position at the moment the signal is transmitted, contacts adapted to be closed by said cam when the cam has rotated to a point representing a given depth, means including said amature to actuate the alarm if the said contacts close prior to the actuation of the armature of the first circuit and to prevent the aciiation of the alarm if the contacts close after the actuation of the armature.

l 5. In an interval meter of the type adapted to be actuated by the sending of a signal and the receipt of it's echo, an alarm, a rst relay and circuit therefor, cam controlled means actuated in timed relation with the sending of the signal to :actuate the relay at theend of a definite period of time after the signal is sent, a second relay and circuit therefor, means to control the second relay by the receipt of the echo, a circuit to said alarm controlled by said second relay, the armature of the rst relay serving as a means to close the circuit for the second relay when the first relay is not actuated, and to break the circuit to the second relay when the first relay is actuated.

6. In an interval meter of the type adapted to be actuated by the sending of a signal and the receipt of the echo, an alarm, a first relay and circuit therefor, cam controlled means` -actuated in timed relation with the sending of the signal to actuate the relay at the end of a definite period of time after the signal is sent, a second relay and circuit therefor, means to control the second relay by the receipt of the echo, a circuit to said alarm controlled by said second relay, the armature. of the first relay serving as a means to close the circuit for the second relay when the first relay is not actuated, and to break the circuit to the second relay when the first relay is actuated, and means to maintain the rst relay in its actuated condition from the time of its actuation to the end of a predetermined period of time.

7. In a time interval meter acting on the echo principle, a rst relay, cam controlled means actuated in timed relation with the sending of the signal whereby the said first relay is actuated at the end of a. definite period of time after the signal is sent and is thereafter maintained actuated until reset, an alarm, a circuit to said alarm, a second relay to control said alarm circuit, a circuit to said second relay. means whereby the circuit to said second relay is closed when the echo is received prior to the actuation of the rst relay,'and is opened when the echo is received after the actuation of the first relay.

8. In a time interval meter acting on the echo principle, means to send out a signal, a rst relay, means whereby the said rst relay is actuated at the end of a predetermined time interval after the signal is sent and is thereafter maintained actuated until reset, an alarm, a circuit to said alarm, a second relay to control said alarm circuit, a circuit to said second relay, means whereby the circuit to said second relay is closed when the echo is received prior to the actuation of the first relay, and is opened when the echo is received after the actuation of the rst relay, and means whereby the second relay maintains the alarm energie circuit closed after the second relay is actuated until reset.

9. In a time interval meter acting on the echo principle, means to send out a signal, a rst relay, means whereby the said first relay is actuated at the end of a predetermined time interval after the signal is sent and is thereafter maintained actuated until reset, yan alarm, a circuit to said alarm, a second relay to control said alarm circuit, a circuit to said second relay, means whereby the circuit to said second relay is closed when the echo is received prior to the actuation of the first relay, |and is opened when the echo is received after the actuation of the first relay, means whereby the second .relay maintains the alarm circuit closed after the second relay is actuated until reset, and means to reset both of said relays after the end of a predetermined time interval.

10. In a depth finder in which signals are sent out by a transmitter and the echo is received by a receiver, the interval between two successive signals being one cycle, a deep alarm, a relay circuit adapted to be set for a predetermined depth, means controlled by the relay circuit to cause the alarm to be actuated when no echo has been received during a time interval corresponding to said predetermined depth, means whereby the alarm when operated continues to be operated Y until the relay circuit is reset and means to reset the relay circuit near the expiration of the cycle.

11. In a depth finder in which signals are sent out by a transmitter and the echo is received by a receiver, the interval between two successive signals being one cycle, a deep alarm, a relay circuit adapted to be set for a predetermined depth, means controlled by the relay circuit to cause the alarm to be actuated when no echo has been received during a time interval corresponding to said predetermined depth, means whereby the alarm when operated continues to be operated until the relay circuit is reset, means to inhibit the operation of the alarm when the echo is received from a depth less than the predetermined depth, and means to reset the relay circuit near the expiration of the cycle.

TIMOTHY FRANKLIN BLUDWORTI-I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 160,400 Dixwell Mar. 2, 1875 1,007,178 Billings Oct. 31, 1911 1,547,909 Earle July 28, 1925 1,729,595 Hayes Sept. 24, 1929 1,853,119 Fessenden Apr. 12, 1932 1,885,652 Touly Nov, 1, 1932 1,968,078 Hershey July 31, 1934 2,007,371 Hopkins et al. July 9, 1935 2,009,459 Turner July 30, 1935 2,012,837 Tear Aug. 27, 1935 2,098,266 Walker Nov. 7, 1937 FOREIGN PATENTS Number Country Date 684,321 Germany Nov. 25, 1939 

